INDUSTRIAL AND ENGINEERING CHEMISTRY
910
the range of control due to the movement of mercury extended from 1 to 350 mm.; without the air pocket the range was from 1 to 220 mm. Besides increasing the effective range of the regulator 100 mm., the air pocket helps to prevent the breaking of the glass arm by the mercury if the pressure in the system suddenly increases. No rubber tubing is used in the regulator itself. Since connection to the system is made close to the fulcrum, heavy pressure tubing may be used without interfering with the action of the regulator. If gases other than air are desired in the system during a distillation, the apparatus shown in Figures 5 and 6 may be added. This addition is facilitated by the relatively little movement between the capillary and the rubber stopper. If side arms D and E are left open to the air, air will be drawn into the system, but if nitrogen or carbon dioxide is passed through D and out E, these gases will be drawn into the system instead. Before starting a distillation the system should be flushed out with the gas to be used by applying a vacuum and having the capillary open as much as possible. The glass collar is fastened to the capillary by a short length of rubber tubing, G. A glass-to-glass seal is better, since no flexibility is desired at this point. Rubber stopper H ,
Vol. 13, No. 12
forming the valve seat, was cut halfway through with a cork borer and then the outside portion was cut away with a razor as shown in Figure 5 . Two No. 8 rubber stoppers were bored to fit G and H , respectively, and a 4-mm. section was taken from the bottom of each. They were fastened together with a short length of Gooch rubber tubing t o provide free movement between the capillary and rubber valve seat. In Figure 7 the same effect is accomplished using a mercury seal. This is much more rugged and easily handled, but a sudden increase of nitrogen or carbon dioxide pressure might blow out the mercury.
Acknowledgment The author wishes to acknowledge the helpful encouragement of P. A. van der Meulen and D. L. Cottle. Appreciation is also due F. G. Horstmann, Bellerille, N. J., for the unlimited use of his machine shop
Literature Cited (1) Schierholtz, 0. J., IND.ENG.CHEU.,\SAL. ED.,7, 284 (1935)
Disposal of Acid Fumes in Wet Assaying EDGAR J. POTH AND GEORGE A . ELLIOTT Surgical Hunterian Laboratory, Department of Surgery, The Johns Hopkins School of >Iedicine, Baltimore, Md.
W
ORKERS in old or improvised laboratories are frequently confronted with the problem of disposal of acid fumes from wet-assay digestions. If the fume-laden gases are passed through zeolite sand covered with water, the fumes are effectively removed. The surface afforded by the grains of sodium aluminum silicate adsorbs and reacts with the fumes rapidly and completely and allows relatively large volumes of inert gas to be passed without the passage of the acid fumes. The fumes are removed so completely that any type of evacuating pump can be employed with the exhaust open to the laboratory. The commercial grade of synthetic zeolite sand gradually
dissolves and passes off with the condensed overflow. The absorbent is most economical. The application of this procedure t'o micro-Kjeldahl digestion is illustrated in Figure 1. Bottle B contains zeolite sand covered with water. A acts as a trap for sand grains from B. A spray trap, C, employing the indentations featured in the Vigreux type of fractionating head, drains well and efficiently breaks up the spray. The tip, D, drains the side arm and prevents the formation of fluid locks in the system, which would cause fumes to escape at the open connect,ions. A trap, C, fits into the mouth of each digestion tube or flask and serves t o prevent loss of sample in the spray and t o connect the digestion vessel to the fume-absorbing system.
7
TO EVACUATING PUMP -28
SIDE E L E V A T I O N
TOP E L E V A T I O N
FIGURE
1.
1
END ELEVATION
SPRAY TRAP
u I
DIGESTION RACKFOR
_.
MICRO-KJELDIHL
DETERMINATIONS
